Contents lists available at ScienceDirect Journal of CO 2 Utilization journal homepage: www.elsevier.com/locate/jcou Use of hot supercritical CO 2 produced from a geothermal reservoir to generate electric power in a gas turbine power generation system Edward K. Levy a , Xingchao Wang a, ⁎ , Chunjian Pan a , Carlos E. Romero a , Carlos Rubio Maya b a Energy Research Center, Lehigh University, 117 ATLSS Drive, Bethlehem, PA 18015, USA b Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico ARTICLE INFO Keywords: Supercritical carbon dioxide Geothermal heat mining Power generation ABSTRACT CO 2 capture and sequestration in deep saline aquifers is widely considered to be a leading option for controlling greenhouse gas emissions. One such possibility involves injection of supercritical carbon dioxide into a high- permeability geothermal reservoir. In addition to the benefit of sequestering the CO 2 in the reservoir, the CO 2 can be used to mine geothermal heat for utilization above ground. This paper describes one of the options for generating power from hot supercritical CO 2 obtained from CO 2 production wells connected to a geothermal reservoir, where the original source of the CO 2 is CO 2 captured from fossil-fired power plants or industrial processes. The cost of power generated using CO 2 produced from a geothermal reservoir with a gas turbine generation system is compared to the cost of generating power from a conventional geothermal steam power plant. 1. Introduction Carbon capture and sequestration is widely recognized as one of the more promising methods for preventing CO 2 formed in fossil-fired power plants or industrial processes from being released into the at- mosphere. Fig. 1 shows a fossil-fired power plant with a post combus- tion carbon capture system, with the captured CO 2 compressed to su- percritical pressures and then injected into a porous geologic reservoir for long term storage. Over the last few decades, numerous in- vestigators have been developing a variation of the CCS approach shown in Fig. 1, in which compressed CO 2 from a carbon capture process is injected into a hot geothermal reservoir. The heated high pressure CO 2 flows through production well(s) to the surface of the earth. It then flows into a CO 2 -water separator and from there into a power generation system and it is then reinjected into the reservoir for ultimate sequestration (Fig. 2). These investigations have resulted in publications describing studies of the fluid flow and heat transfer pro- cesses in injection and production wells and through the porous ma- terial in the reservoir [1–9], papers describing the importance of CO 2 thermosiphons which occur due to injection of cold supercritical CO 2 into geothermal reservoirs and production of hot pressurized CO 2 from the reservoirs to the earth’s surface [10–13], and papers dealing with the use of either Organic Rankine Cycle power systems or power sys- tems which rely on expansion of hot pressurized CO 2 through turbines to generate electric power from the hot produced CO 2 [14–16]. Also pertinent are publications dealing with production of water from geologic reservoirs to control reservoir pressure during CO 2 in- jection, to recover water from the reservoir for subsequent use in water scarce areas, and/or to control the CO 2 production process [17–20]. The present paper describes analyses which link the pressure and flow rate of the CO 2 injected into a geologic reservoir, the arrangement of the injection and production wells, and the pressure, temperature and flow rate of the produced CO 2 to the power generated from Direct Turbine Expansion Power Generation Systems. In addition, results from thermoeconomic analyses are presented to compare the cost of power generated from CO 2 -based geothermal power systems to the cost of power generated by a steam cycle geothermal power plant. 2. Reservoir and well modeling of CO 2 flow rate, temperature and pressure The inputs needed for the type of power plant performance and cost analyses described in this paper include information on the tempera- ture, pressure and flow rate of the hot CO 2 at the production well head and pressure and temperature at the injection well head. Simulations, using an analytic expression for the Darcy Law for CO 2 pressure drop in the reservoir in combination with the T2Well/ECO2N code [21], were performed for a system of five wells arranged as shown in Fig. 3. It was assumed that the top and bottom of the reservoir were 2000 m and 2500 m below the surface of the earth, the horizontal distance between https://doi.org/10.1016/j.jcou.2017.11.001 Received 9 June 2017; Received in revised form 11 October 2017; Accepted 8 November 2017 ⁎ Corresponding author. E-mail address: xiw611@lehigh.edu (X. Wang). Journal of CO₂ Utilization 23 (2018) 20–28 2212-9820/ © 2017 Elsevier Ltd. All rights reserved. MARK